Alignment Guides With Patient-Specific Anchoring Elements

ABSTRACT

A method for preparing a bone of a joint during joint arthroplasty. The method includes mounting an alignment guide on the bone of a patient along an alignment direction. The method further includes anchoring the alignment guide into a cartilage of the bone using a plurality of patient-specific anchoring elements extending from an inner surface of alignment guide, each anchoring element having a patient-specific length extending between the inner surface and an end point of the corresponding anchoring element.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.13/041,495, filed on Mar. 7, 2011, which claims the benefit of U.S.Provisional Application No. 61/446,660, filed on Feb. 25, 2011 and is acontinuation-in-part of U.S. application Ser. No. 12/973,214, filed Dec.20, 2010, which is a continuation-in-part of U.S. application Ser. No.12/955,361 filed Nov. 29, 2010, which is a continuation-in-part of U.S.application Ser. Nos. 12/938,905 and 12/938,913, both filed Nov. 3,2010, each of which is a continuation-in-part of U.S. application Ser.No. 12/893,306, filed Sep. 29, 2010, which is a continuation-in-part ofU.S. application Ser. No. 12/888,005, filed Sep. 22, 2010, which is acontinuation-in-part of U.S. application Ser. No. 12/714,023, filed Feb.26, 2010, which is: a continuation-in-part of U.S. application Ser. No.12/571,969, filed Oct. 1, 2009, which is a continuation-in-part of U.S.application Ser. No. 12/486,992, filed Jun. 18, 2009, and is acontinuation-in-part of U.S. application Ser. No. 12/389,901, filed Feb.20, 2009, which is a continuation-in-part of U.S. application Ser. No.12/211,407, filed Sep. 16, 2008, which is a continuation-in-part of U.S.application Ser. No. 12/039,849, filed Feb. 29, 2008, which: (1) claimsthe benefit of U.S. Provisional Application No. 60/953,620, filed onAug. 2, 2007, U.S. Provisional Application No. 60/947,813, filed on Jul.3, 2007, U.S. Provisional Application No. 60/911,297, filed on Apr. 12,2007, and U.S. Provisional Application No. 60/892,349, filed on Mar. 1,2007; (2) is a continuation-in-part U.S. application Ser. No.11/756,057, filed on May 31, 2007, which claims the benefit of U.S.Provisional Application No. 60/812,694, filed on Jun. 9, 2006; (3) is acontinuation-in-part of U.S. application Ser. No. 11/971,390, filed onJan. 9, 2008, which is a continuation-in-part of U.S. application Ser.No. 11/363,548, filed on Feb. 27, 2006; and (4) is acontinuation-in-part of U.S. application Ser. No. 12/025,414, filed onFeb. 4, 2008, which claims the benefit of U.S. Provisional ApplicationNo. 60/953,637, filed on Aug. 2, 2007.

This application is a divisional of U.S. application Ser. No.13/041,495, filed on Mar. 7, 2011, which is a continuation-in-part ofU.S. application Ser. No. 12/872,663, filed on Aug. 31, 2010, whichclaims the benefit of U.S. Provisional Application No. 61/310,752 filedon Mar. 5, 2010.

This application is a divisional of U.S. application Ser. No.13/041,495, filed on Mar. 7, 2011, which is a continuation-in-part ofU.S. application Ser. No. 12/483,807, filed on Jun. 12, 2009, which is acontinuation-in-part of U.S. application Ser. No. 12/371,096, filed onFeb. 13, 2009, which is a continuation-in-part of U.S. application Ser.No. 12/103,824, filed on Apr. 16, 2008, which claims the benefit of U.S.Provisional Application No. 60/912,178, filed on Apr. 17, 2007.

This application is a divisional of U.S. application Ser. No.13/041,495, filed Mar. 7, 2011, which is also a continuation-in-part ofU.S. application Ser. No. 12/103,834, filed on Apr. 16, 2008, whichclaims the benefit of U.S. Provisional Application No. 60/912,178, filedon Apr. 17, 2007.

This application is a divisional of U.S. application Ser. No.13/041,495, filed Mar. 7, 2011, which is also a continuation-in-part ofU.S. application Ser. No. 12/978,069, filed Dec. 23, 2010, which is acontinuation-in-part of U.S. application Ser. No. 12/973,214, filed Dec.20, 2010.

The disclosures of the above applications are incorporated herein byreference.

INTRODUCTION

The present teachings provide various alignment guides withpatient-specific anchoring elements for joint arthroplasty.

SUMMARY

The present teachings provide for a method for preparing a bone of ajoint during joint arthroplasty. The method includes mounting analignment guide on a bone of a joint of a patient along an alignmentdirection; and anchoring the alignment guide into a cartilage of thebone using a plurality of patient-specific anchoring elements extendingfrom an inner surface of alignment guide, each anchoring element havinga patient-specific length extending between the inner surface and an endpoint of the corresponding anchoring element.

The present teachings further provide for a method for preparing a boneof a joint during joint arthroplasty including: mounting an alignmentguide on an outer cartilage surface of an articular cartilage of anunderlying bone of the patient; anchoring the alignment guide on thepatient's anatomy using a plurality of patient-specific anchoringelements extending from a cartilage-engaging surface of alignment guide;penetrating the cartilage with cartilage-engaging portions of theanchoring elements, each cartilage-engaging portion having a lengthextending between first and second ends; and penetrating an outer bonesurface of the underlying bone with bone-engaging portions of theanchoring elements.

The present teachings still further provide for a method for preparing abone of a joint during joint arthroplasty. The method includes mountingan alignment guide on a bone of a joint of a patient along an alignmentdirection; and positioning the aligning guide such that a plurality ofpatient-specific anchoring elements extending from an inner surface ofthe alignment guide penetrate through an outer cartilage surface of thebone and penetrate through the outer bone surface of the bone foranchoring the alignment guide on the bone of the patient, each anchoringelement having a patient-specific length extending between the innersurface and an end point of the corresponding anchoring element.

Further areas of applicability of the present teachings will becomeapparent from the description provided hereinafter. It should beunderstood that the description and specific examples are intended forpurposes of illustration only and are not intended to limit the scope ofthe present teachings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present teachings will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a plan view of a patient-specific alignment guide withanchoring elements according to the present teachings;

FIG. 2 is an environmental sectional view of a patient-specificalignment guide with anchoring elements according to the presentteachings;

FIG. 3 is an environmental perspective view of a patient-specificfemoral alignment guide with anchoring elements according to the presentteachings;

FIG. 4 is an environmental perspective view of a patient-specific tibialguide with anchoring elements according to the present teachings;

FIG. 5 is an environmental sectional view of a patient-specificalignment guide with anchoring elements according to the presentteachings;

FIG. 5A is a detail of an anchoring element of FIG. 5;

FIG. 6 is an environmental perspective view of a patient-specificfemoral alignment guide with anchoring elements according to the presentteachings; and

FIG. 7 is an environmental perspective view of a patient-specific tibialguide with anchoring elements according to the present teachings.

DESCRIPTION OF VARIOUS ASPECTS AND EMBODIMENTS

The following description is merely exemplary in nature and is in no wayintended to limit the present teachings, applications, or uses.

The present teachings generally provide various patient-specificalignment and resection guides and other associated instruments for usein orthopedic surgery, such as, for example, in joint replacement orrevision surgery. The patient-specific guides can be used either withconventional or patient-specific implant components and can be preparedwith computer-assisted image methods. Computer modeling for obtainingthree-dimensional (3-D) images of the patient's anatomy using MRI or CTscans of the patient's anatomy, modeling of patient-specific prosthesiscomponents and the patient-specific guides and templates can beconfigured and designed using various commercial CAD programs and/orsoftware, such as, for example, software by Materialise USA, Ann Arbor,Mich.

Patient-specific alignment guides and implants are generally configuredto match the anatomy of a specific patient. The patient-specificalignment guides are generally formed using computer modeling based onthe patient's 3-D anatomic image and have an engagement surface that ismade to conformingly contact and match a three-dimensional image of thepatient's bone surface (with or without cartilage or other soft tissue)in only one position, by the computer methods discussed above. Thepatient-specific alignment guides are designed and preparedpreoperatively using anatomic landmarks, such as osteophytes, forexample, and can be mounted intra-operatively without any registrationor other guidance based on their unique patient-specific surface guidedby the patient's anatomic landmarks.

The patient-specific alignment guides can include custom-made guidingformations, such as, for example, guiding bores or cannulated guidingposts or cannulated guiding extensions or receptacles that can be usedfor supporting or guiding other non-custom instruments, such as drillguides, reamers, cutters, cutting guides and cutting blocks or forinserting pins or other fasteners according to a surgeon-approvedpre-operative plan for performing various resections as indicated for anarthroplasty, joint replacement, resurfacing or other procedure for thespecific patient.

The patient-specific guides can also include resection or cuttingformations, such as cutting slots or cutting edges or planes used forguiding a cutting blade to perform bone resections directly through thepatient-specific cutting guide. The patient-specific guides can be usedin minimally invasive surgery. Various alignment/resection guides andpreoperative planning procedures are disclosed in commonly assigned andco-pending U.S. patent application Ser. No. 11/756,057, filed on May 31,2007; U.S. patent application Ser. No. 12/211,407, filed Sep. 16, 2008;U.S. patent application Ser. No. 11/971,390, filed on Jan. 9, 2008, U.S.patent application Ser. No. 11/363,548, filed on Feb. 27, 2006; and U.S.patent application Ser. No 12/025,414, filed Feb. 4, 2008. Thedisclosures of the above applications are incorporated herein byreference.

As disclosed, for example, in the above-referenced U.S. patentapplication Ser. No. 11/756,057, filed on May 31, 2007, in thepreoperative planning stage for a joint replacement or revisionprocedure, an MRI scan or a series of CT scans of the relevant anatomyof the patient, such as, for example, the entire leg of the joint to bereconstructed, can be performed at a medical facility or doctor'soffice. The scan data obtained can be sent to a manufacturer. The scandata can be used to construct a three-dimensional image of the joint andprovide an initial implant fitting and alignment in a computer file formor other computer representation. The initial implant fitting andalignment can be obtained using an alignment method, such as alignmentprotocols used by individual surgeons.

The outcome of the initial fitting is an initial surgical plan that canbe printed or provided in electronic form with corresponding viewingsoftware. The initial surgical plan can be surgeon-specific, when usingsurgeon-specific alignment protocols. The initial surgical plan, in acomputer/digital file form associated with interactive software, can besent to the surgeon, or other medical practitioner, for review. Thesurgeon can incrementally manipulate the position of images of variousimplant components in an interactive image of the joint. Additionally,the surgeon can select or modify resection planes, types of implants andorientations of implant insertion. After the surgeon modifies and/orapproves the surgical plan, the surgeon can send the final, approvedplan to the manufacturer.

After the surgical plan is approved by the surgeon, patient-specificalignment/resection guides can be designed by configuring and using aCAD program or other imaging software, such as the software provided byMaterialise, for example, according to the surgical plan. Computerinstructions of tool paths for machining the patient-specific alignmentguides can be generated and stored in a tool path data file. The toolpath can be provided as input to a CNC mill or other automated machiningsystem, and the alignment guides can be machined from polymer, ceramic,metal or other suitable material. The guides can also be manufactured byvarious other methods, stereolithography, laser deposition, printing,and rapid prototyping methods. The alignment guides are sterilized andshipped to the surgeon or medical facility, for use during the surgicalprocedure. Various patient-specific knee alignment guides and associatedmethods are disclosed in the commonly assigned U.S. application Ser. No.11/756,057, filed on May 31, 2007 (published as 2007/0288030 on Dec. 13,2007), which is incorporated herein by reference.

A patient-specific alignment guide can be used to drill holes throughcorresponding bone of the joint surface and to guide alignment pinsthrough the holes. The alignment guide is then removed leaving thealignment pins for supporting and cutting instruments to make variousresections in the bone in preparation for receiving a joint implant.

The various patient-specific alignment guides can be made of anybiocompatible material, including, polymer, ceramic, metal orcombinations thereof. The patient-specific alignment guides can bedisposable and can be combined or used with other reusable nonpatient-specific cutting and guiding components.

Referring to FIGS. 1 and 2, an exemplary alignment guide 100 isgenerally illustrated according to the present teachings. The alignmentguide 100 has a three-dimensional, curved inner surface 102. In someembodiments, the inner surface 102 nestingly matches and iscomplementary to a corresponding surface of a patient including variousanatomic landmarks, such that the alignment guide 100 can be positionedand nested only in one position relative to the anatomy of the specificpatient along an alignment orientation A. The patient's anatomy can be,for example, a bone 80 related to a joint of the patient and including alayer of articular cartilage 83 over an outer bone surface 82. Thearticular cartilage 83 can extend between the outer bone surface 82 andan outer cartilage surface 84. In this embodiment, the inner surface 102of the patient-specific guide 100 is designed to match and mate with theouter cartilage surface 84. The alignment guide 100 is designed to belight-weight and can include various cut-outs or windows, such as 104.The alignment guide 100 can include a plurality of patient-specificanchoring elements 111 with end points 113. The anchoring elements 111can be, for example, spikes, or teeth or pins extending from theanatomy-engaging surface 102 and sized and configured to penetrate thecartilage up to the outer bone surface 82. The anchoring elements 111can be engage the cartilage 83 at several points for providingthree-dimensional anchoring stability. Multiple anchoring elements 111,such as, for example, five or more, can be positioned uniformly orrandomly relative to the inner surface 102. Alternatively, a fewanchoring elements 111, such as, for example about three to five, can beincluded at selected or pre-determined and relative positions.

In some embodiments, the anchoring elements 111 can be configured to beparallel to an alignment/mounting direction A for mounting and removingthe guide 100, as shown in FIG. 2. Using parallel anchoring elements 111can avoid tearing the cartilage and thereby reducing the anchoringstability of the alignment guide 100. The alignment/mounting directioncan be determined during the preoperative plan for the patient. In someembodiments, the three-dimensional shape of the outer bone surface 82(and, optionally, the outer cartilage surface 84) can be represented inthree-dimensional computer models generated from the medical scans ofthe patient and used to design the variable and patient-specific height(or length) of each anchoring element 111 such that a geometric envelopeof the end points 113 traces a surface complementary and mating with theouter bone surface 82. Accordingly, only the outer bone surface 82 needsto be imaged using standard bone imaging methods, such as CT andtwo-dimensional X-rays, for example. Therefore, for these embodiments,is not necessary to use methods, such as MRI, that can image thecartilage or other soft tissue. In some embodiments, the length of theanchoring elements is patient-specific. In some embodiments, the lengthof the anchoring elements 111 can be greater that the correspondingthickness of the cartilage 83, such that the inner surface 102 of thealignment guide 100 does not contact the cartilage.

In some embodiments, each anchoring element 111 can have a lengthextending from the end point 113 to the inner surface 102 andapproximating the thickness of the articular cartilage 83 of theparticular bone 80 of the patient at each specific location of theanchoring element 111. The thickness of the cartilage 83 can generallyvary with the topography of the joint, i.e., the cartilage distributionis non-uniform over a bone surface for a single patient. There may alsobe additional gender-, age-, weight- and disease-related cartilagevariations. The cartilage of a specific patient can also have variousdefects or other idiosyncratic features. A detailed cartilage topographyof a specific patient can be determined during the pre-operative planfrom medical scans/images that can depict bone and soft tissue surfaces,such as, for example, MRI images, CT images or other imaging methodscapable of showing bone and/or soft tissue.

In some embodiments, a uniform and constant height can be selected forall the anchoring elements, equal, for example, to the mean or themedian or maximum or other value based on the thickness variation of thecartilage of a particular joint surface of the patient. When the maximumthickness of the cartilage is used as the height of all the anchoringelements 111, the inner surface 102 of the patient-specific guide 100may not contact points of the outer cartilage surface 84 where thecartilage 83 is thinner than the maximum, i.e., there may be some areasof non-contact forming gaps between the cartilage 83 and theanatomy-engaging surface 102. Depending on the location of the cartilage83, the thickness of the cartilage 103 can vary from 0 to 6-7 mm, withhigher thickness generally corresponding to the knee patella of healthyyoung males. In some embodiments, the inner surface 102 of the guide 100does not engage the cartilage 83 at all.

Referring to FIG. 3, an exemplary femoral alignment guide 200 accordingto the present teachings is configured for use with the patient's distalfemoral bone 80 (an example of the bone 80 of FIG. 2). The femoralalignment guide 200 can have a light-weight body 201 with athree-dimensional inner surface 202. In some embodiments, the innersurface 202 may be a patient-specific engagement surface that iscomplementary and made to closely conform and mate with a portion of theanterior-distal articulating or outer cartilage surface 84 of thepatient's femur 80 based on the pre-operative plan, as described above.The femoral alignment guide 200 can include a window/opening 204 andfirst and second distal guiding formations 206 defining guiding bores207 for guiding corresponding distal alignment pins 220. The femoralalignment guide 200 can also include first and second anterior guidingformations 208 defining guiding bores 209 for drilling holes through thedistal femur 80 and guiding corresponding anterior alignment pins 222.Additionally, the femoral alignment guide 200 can include a plurality ofanchoring elements 211 that are similar to the anchoring elements 111described above in reference to FIG. 2. The anchoring elements 211 arealso designed to penetrate the articular cartilage 83 for preventingsmall rotational and/or translational displacements of the femoralalignment guide 200 during use. The anchoring elements 211 can bedistributed randomly or uniformly to penetrate the entire outercartilage surface 84 which the patient-specific femoral guide 200engages. Alternatively, a few discrete anchoring elements 211 can beused instead, including at least three elements. The anchoring elements211 can be parallel defining an alignment/mounting direction forinserting and removing the femoral alignment guide 200, as discussedabove in connection with FIG. 2, and can engage the cartilage at pointsarranged in a three-dimensional pattern for providing anchoringstability. The length of the anchoring elements 211 can be variable andpatient-specific such that a geometric envelope of their end pointstraces a surface complementary and mating with the outer bone surface82.

Referring to FIG. 4, a representative tibial alignment/resection guide300 is illustrated according to the present teachings. The tibialalignment guide 300 can include a body 301 having a proximal portion303, an anterior portion 305 and a three-dimensional inner surface 302.In some embodiments, the inner surface can be a patient-specific surfacethat is complementary and made to closely conform and mate with aportion of an anterior surface 76 and a portion of a proximal surface orouter cartilage surface 74 of the patient's tibia 70 in only oneposition based on the pre-operative plan. The tibial alignment guide 300can include first and second proximal guiding formations 306 definingguiding bores 307 for corresponding proximal alignment pins or otherfasteners 323. The tibial alignment/resection guide 300 can also includefirst and second anterior guiding formations 308 defining guiding bores309 for corresponding anterior alignment pins or other fasteners 327. Asdiscussed above in connection with alignment guides in general and thefemoral alignment guide 200 in particular, the tibial alignment guide300 can be used to drill reference holes for the corresponding proximaland anterior alignment pins 323, 327, which can then be re-inserted asneeded for each resection and corresponding resection block after thetibial alignment/resection guide 300 is removed. The tibialalignment/resection guide 300 can optionally include a resection guidingslot 310 for guiding a tibial resection according to the pre-operativeplan for the patient. Additionally, the tibial alignment guide 300 caninclude a plurality of anchoring elements 311 that are similar to theanchoring elements 111 described above in reference to FIG. 2. Theanchoring elements 311 are designed to penetrate the tibial cartilage 73for preventing small rotational and/or translational displacements ofthe tibial alignment guide 300 during use. The anchoring elements 311can be distributed randomly or uniformly to penetrate the tibialcartilage 73 between the bone surface 72 and the outer cartilage surface74 of the proximal tibia over the area that the proximal portion 303 ofthe patient-specific tibial alignment guide 300 engages. Alternatively,a few discrete anchoring elements 311 can be used instead, including atleast three elements in a three-dimensional arrangement. Generally, theanchoring elements 311 can be parallel to an alignment/mountingdirection (see FIG. 2) and engage the cartilage at points arranged in athree-dimensional pattern for stability. The length of the anchoringelements 311 can be variable and patient-specific such that a geometricenvelope of their end points traces a surface complementary and matingwith the outer bone surface 72, as discussed above.

Referring to FIGS. 5 and 5A, a detail of an alignment guide 400 withpatient-specific anchoring elements 450 is illustrated according to thepresent teachings. FIG. 6 illustrates a femoral alignment guide 500similar to the femoral alignment guide 200, but with patient-specificanchoring elements 550 similar to the patient-specific anchoringelements 450 of FIG. 5. Similar elements between alignment guides 200and 500 are referenced with numerals having the same second and thirddigits. FIG. 7 illustrates a tibial alignment guide 600 similar to thetibial alignment guide 300, but with patient-specific anchoring elements650 similar to the patient-specific anchoring elements 450 of FIG. 5.Similar elements between alignment guides 300 and 600 are referencedwith numerals having the same second and third digits. Thepatient-specific anchoring elements 450, 550 and 650 are similar and aredescribed in reference to FIG. 5, which illustrates generically aportion of a patient-specific alignment guide 400. At least threeanchoring elements 450 in a three dimensional pattern can be used forproviding anchoring stability in three dimensions. In some embodiments,the alignment guides 400, 500 and 600 can also be patient-specific withthree-dimensional cartilage engaging surfaces that can nestingly mate toand be mounted on the outer surface of the articular cartilage of thepatient in only one position.

The patient-specific anchoring elements 450 can be designed using athree-dimensional computer image of the patient's anatomy including thearticular cartilage surface and the underlying bone during apreoperative plan for the patient. The three-dimensional image can beconstructed based on medical scans of he patient, such as MRI, CT,ultrasound or other scans equipped or modified to image soft tissue,such as articular cartilage and using commercially available CAD/CADimaging software.

Referring to FIGS. 5 and 5A, the patient-specific anchoring elements 450are configured for penetrating the articular cartilage 83 and anchoringinto the underlying bone 80 through the outer bone surface 82. Eachanchoring element 450 can include a cartilage-anchoring portion 452 anda bone-anchoring portion 454. The cartilage-anchoring portion 452 can bein the form of an elongated element having a first end 458 attached toan anatomy-engaging surface 402 of the alignment guide 400 and anopposite second end 456 in the form of a patient-specific surface 460designed for abutting and closely mating with the outer bone surface 82.The geometric envelope of the patient-specific surfaces 460 of all theanchoring elements 450 can be designed during the pre-operative plan tobe patient-specific relative to the outer bone surface 82, such that thesurface 460 to be complementary and closely mate and conform to theouter bone surface 82. Accordingly, the length of eachcartilage-anchoring portion 452 from the first end 458 to the second end456 is patient-specific and can be selected to be equal to the thicknessof the patient's cartilage 83 at the corresponding location for eachanchoring element 450. The bone-anchoring portion 454 can be in the formof a spike or pin extending from the second end 456 of thecartilage-anchoring portion 452 for penetrating the outer bone surface82 and lodging into the bone 80.

With continued reference to FIGS. 5 and 5A, the patient-specific surface460 forms a shoulder or step 463 between the second end 456 of thecartilage-anchoring portion 452 and the bone-anchoring portion 454. Thecartilage-anchoring portion 452 penetrates the cartilage 83 and can beseated in a pocket formed in the cartilage 83 when the alignment guide400 is pressed against the bone 80 until the bone-anchoring portion 454penetrates the bone 80 and the patient-specific surface 460 nestinglymates and seats on the outer bone surface 82 under the cartilage. Thebone anchoring portion 454 can be made of a material of sufficientstrength and/.or rigidity to penetrate the bone 80. In some embodiments,the bone anchoring portion 454 and the cartilage-anchoring portion 452can be made of different materials. In some embodiments, thebone-anchoring portion 454 can be made separately from thecartilage-anchoring portion 452 and have a portion 459 insertedpermanently or removably into the cartilage-anchoring portion 452. Inother embodiments, the bone anchoring portion 454 and thecartilage-anchoring portion 452 can be made as one integral ormonolithic piece. In some embodiments, the anchoring elements can beparallel to an alignment orientation A. In some embodiments, theanchoring elements can be perpendicular to bone surface 82.

With continued reference to FIGS. 5 and 5A, the cartilage-engagingsurface 402 can be designed during the pre-operative plan of the patientas a three-dimensional patient-specific surface that complementarily andnestingly mates with the outer cartilage surface 84 in only oneposition. In some embodiments, conformance to small variations, such asminute defects, in the outer cartilage surface 84 may be relaxed,although the alignment guide 400 can still be mounted on the outercartilage surface in only one position and is still patient-specific. Inthis respect, a small gap “g” may be formed between the outer cartilagesurface 84 and the anatomy-engaging surface 402 of the alignment guide400 in certain locations depending on the profile and condition of thecartilage 83. The cartilage-anchoring portion 452 of each anchoringelement 450 has a patient specific length and a patient-specificbone-abutting surface 460. The cartilage-anchoring portion 452 cangenerally have a diameter or major cross-sectional dimension of about2-5 mm, while the major cross-sectional dimension of the bone-anchoringportion 454 can be about 1-2 mm. The gap g can also be of the order of1-2 mm.

As discussed above, the patient-specific anchoring elements 111, 211,311, 450, 550, 650 can be integrated with various patient-specificguides designed to engage a cartilage bearing articulating surface of ajoint, such as the distal femur and the proximal tibia for a knee joint.The patient-specific anchoring elements can also be used, for example,with guides designed to engage the articular surfaces of the hip jointor shoulder joint.

The foregoing discussion discloses and describes merely exemplaryarrangements of the present teachings. Furthermore, the mixing andmatching of features, elements and/or functions between variousembodiments is expressly contemplated herein, so that one of ordinaryskill in the art would appreciate from this disclosure that features,elements and/or functions of one embodiment may be incorporated intoanother embodiment as appropriate, unless described otherwise above.Moreover, many modifications may be made to adapt a particular situationor material to the present teachings without departing from theessential scope thereof. One skilled in the art will readily recognizefrom such discussion, and from the accompanying drawings and claims,that various changes, modifications and variations can be made thereinwithout departing from the spirit and scope of the present teachings asdefined in the following claims.

What is claimed is:
 1. A method for preparing a bone of a joint duringjoint arthroplasty comprising: mounting an alignment guide on the boneof a patient along an alignment direction; and anchoring the alignmentguide into a cartilage of the bone using a plurality of patient-specificanchoring elements extending from an inner surface of alignment guide,each anchoring element having a patient-specific length extendingbetween the inner surface and an end point of the correspondinganchoring element.
 2. The method of claim 1, wherein the end points ofthe anchoring elements define a geometric envelope that traces an outersurface of the bone.
 3. The method of claim 1, wherein the anchoringelements are parallel to the alignment direction.
 4. The method of claim1, further comprising customizing the plurality of patient-specificanchoring elements based on imaging of a particular patient's anatomy.5. The method of claim 1, wherein the inner surface is athree-dimensional patient-specific surface including a customized shapebased on a multi-dimensional image of an outer cartilage surface of thebone of the patient and configured to nestingly mate to and be mountedon the outer cartilage surface of the bone of the patient in only oneposition.
 6. The method of claim 1, further comprising positioning thealigning guide such that the anchoring elements penetrate through anouter cartilage surface of the bone and penetrate through the outer bonesurface of the bone to anchor the alignment guide on the bone of thepatient.
 7. The method of claim 6, wherein each anchoring elementincludes a patient-specific cartilage-anchoring portion and abone-anchoring portion, the cartilage-anchoring portion having first andsecond ends, the first end extending from the inner surface of thealignment guide, the bone-anchoring portion extending from a portion ofthe second end of the cartilage-anchoring portion.
 8. The method ofclaim 1, further comprising mounting and anchoring the alignment guideto a distal femoral bone.
 9. The method of claim 1, further comprisingmounting and anchoring the alignment guide to a proximal tibial bone.10. A method for preparing a bone of a joint during joint arthroplastycomprising: mounting an alignment guide on an outer cartilage surface ofan articular cartilage of an underlying bone of the patient; anchoringthe alignment guide on the patient's anatomy using a plurality ofpatient-specific anchoring elements extending from a cartilage-engagingsurface of alignment guide; penetrating the cartilage withcartilage-engaging portions of the anchoring elements, eachcartilage-engaging portion having a length extending between first andsecond ends; and penetrating an outer bone surface of the underlyingbone with bone-engaging portions of the anchoring elements.
 11. Themethod of claim 10, further comprising abutting and mating the outercartilage surface of the bone with shoulder surfaces of thecartilage-engaging portions of the anchoring elements.
 12. The method ofclaim 10, further comprising determining patient-specific lengths of thecartilage-engaging portions of the anchoring elements from the cartilagethickness at corresponding locations of the bone of the patient.
 13. Themethod of claim 12, further comprising determining the cartilagethickness from a three-dimensional computer image of the bone andarticular cartilage reconstructed from medical scans of the patientduring a preoperative plan for the patient.
 14. The method of claim 10,further comprising nestingly mating a three-dimensional patient-specificcartilage engaging surface of the alignment guide on the outer cartilageof the patient in only one position.
 15. The method of claim 10, whereinthe inner surface is a three-dimensional patient-specific surfaceincluding a customized shape based on a multi-dimensional image of anouter cartilage surface of the bone of the patient and configured tonestingly mate to and be mounted on the outer cartilage surface of thebone of the patient in only one position.
 16. A method for preparing abone of a joint during joint arthroplasty comprising: mounting analignment guide on the bone of a patient along an alignment direction;and positioning the aligning guide such that a plurality ofpatient-specific anchoring elements extending from an inner surface ofthe alignment guide penetrate through an outer cartilage surface of thebone and penetrate through an outer bone surface of the bone foranchoring the alignment guide on the bone of the patient, eachpatient-specific anchoring element having a patient-specific lengthextending between the inner surface and an end point of thecorresponding anchoring element.
 17. The method of claim 16, wherein theinner surface is a three-dimensional patient-specific surface includinga customized shape based on a multi-dimensional image of the outercartilage surface and configured to nestingly mate to and be mounted onthe outer cartilage surface in only one position.
 18. The method ofclaim 16, further comprising abutting and mating the outer cartilagesurface of the bone with shoulder surfaces of cartilage-engagingportions of the anchoring elements.
 19. The method of claim 16, furthercomprising customizing the plurality of patient-specific anchoringelements based on imaging of the patient's own anatomy.
 20. The methodof claim 16, further comprising determining patient-specific lengths ofthe cartilage-engaging portions of the anchoring elements from cartilagethickness at corresponding locations of the bone of the patient.